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PLEASE NOTE: |
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The following presentation is designed to be
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Ö Notes displayed. |
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When Notes are displayed, please click on
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All images and text are Copyright Peter
Birtwhistle unless otherwise indicated. |
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Peter Birtwhistle |
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Great Shefford Observatory |
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http://www.birtwhistle.org/ |
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Asteroids & Remote Planets Section
Meeting |
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2nd June 2007 |
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0h Discovery by big Surveys (LINEAR,
Catalina etc.) |
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6Þ12h MPC post prediction on NEO Confirmation
Page (NEOCP) |
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NEOCP confirmation and follow-up |
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Follow-up during discovery apparition |
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Watch for uncertainties to rise (MPC NEAObs
page) |
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Check if still visible by next dark of the moon |
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Catch as moon waxes |
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Recovery at 2nd or subsequent
apparitions |
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Positions on two nights needed to confirm… |
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Objects marked as ‘[1 nighter]’ until
observations span more than ~12 hours |
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If posted on NEOCP quickly can get follow-up
from USA on discovery night but not common… |
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Positional uncertainties increase rapidly if
fast moving discoveries are not confirmed quickly |
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Example: AO18761 |
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discovered by LINEAR 2004 May 24 05:00 UT at mag
+18.8, motion 34”/min |
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Added to NEOCP 14 hours later at 18:48 UT |
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By 2004 21:00 UT mag +19.3 motion 24”/min |
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Discovered by LINEAR 06:58 UT 11 July 2005 |
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Added to the NEOCP 40 hours later… |
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Magnitude 16-17 and moving at 50”/min |
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By then uncertainty area 9° x 0.3° and growing
fast |
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Telescope/CCD field of view 0.3° x 0.3° – a big
search required… |
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Take many relatively short exposure images |
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Digitally combine on the pc using the known
speed and direction of the moving object to build up image |
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If motion turns out to be wrong then re-stack… |
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Astrometrica ( astrometrica) |
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2004 TD18 21/22 October 2004 |
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20 - 50”/min several times a month |
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50 - 250”/min once every month or two (FMOs –
Fast Moving Objects) |
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250”/min or faster, VFMOs |
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Take very short exposures to freeze motion –
don’t measure ends of trails |
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Take as many exposures as possible during
passage across field of view |
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Take a number of separate passages through field
of view |
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Even for bright objects use track & stack |
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Point telescope using mid-time: |
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At speeds over ~60”/min PC timing issues become
very important, so… |
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Need start time of exposure accurate to better
than 1 second of time, but… |
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PC clocks can drift badly and … |
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CCD software normally records time (from PC)
only to nearest second… |
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At Great Shefford |
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Dimension4 freeware used to synchronise time
across the internet (broadband) |
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Software used to wait for the second of the PC
clock to change before starting each exposure |
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Use distant artificial satellites |
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Speeds from 20 – 7000+ ”/min (!) available most
nights |
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Tests internal consistency and procedures, NOT
absolute accuracy of astrometry |
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Most are (relatively) bright |
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Minor Planet Center provides ephemerides for
1983-020A, 1983-020D, Geotail and IMP8 at: |
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Normally very small, only bright enough to be
discovered when already close to Earth |
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Often very little lead time before closest
approach |
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Watch NEOCP for telltale signs – fast
acceleration within 24 hours |
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Try to catch as early as possible on night of
close approach – uncertainties grow quickly |
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VFMOs find you, you don’t find them! |
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VFMOs find you, you don’t find them! |
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When to chase and when to ignore? |
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Must notice in real-time |
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Reduce exposure length and shift telescope to
keep up for first few minutes or longer if possible |
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Measure positions, preferably not ends of trails |
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Use Sat_ID for quick ID of known ART SATs |
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Use FindOrb to work out orbit (or simple
extrapolation) and extend ephemeris to keep following… |
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Artificial satellite or NEO?! |
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Notes